The purpose of this study is to explore the possible role of taurine in the light excitation process and in the generation and transmission of nerve impulse in retina. This investigation would be carried out essentially by measuring the movements of taurine across cell membrane during experimental conditions which simulate the ionic changes underlying retinal excitation. The effect of light stimulation, depolarizing stimulus and some factors influencing ionic balance and ionic distribtion on the release of taurine will be studied. The influence of taurine on ionic transmembrane gradients will be examined following its effect on the kinetics of potassium and calcium efflux. Initial studies will be carried out in isolated, perfused whole retina; thereafter, experiments will be conducted on subcellular structures of retina isolated by density gradient centrifugation; outer and inner segments of photoreceptors, photoreceptor terminals and conventional nerve endings. Similar experiments will be carried out in retinas where experimental degenerations of specific cell layers have been produced. The information obtained will contribute to a better understanding of the role of the high concentrations of taurine present in retina.